[client] fix build: add ReapplyMatching to dedicated AllowedIPsRefCounter (#6935)

## Describe your changes

#6799 turned `AllowedIPsRefCounter` from an alias of the generic
`Counter` into a dedicated peer-aware type. A change merged in parallel
— `DefaultManager.ReconcilePeerAllowedIPs` (lazy-connection idle→wake
reconvergence) — calls `allowedIPsRefCounter.ReapplyMatching`, which
only existed on the generic `Counter`. Each PR built alone; the merged
`main` did not:

```
client/internal/routemanager/manager.go: m.allowedIPsRefCounter.ReapplyMatching undefined
```

Add `ReapplyMatching(pred, apply)` to the dedicated type, matching the
generic contract (keyed on the active/`Out` peer): it re-applies every
prefix whose currently installed peer satisfies `pred`, skipping
prefixes with no active peer (reconciled by the next
Increment/Decrement). Also update `reconcile_test.go` to construct the
counter via `refcounter.NewAllowedIPs` — the generic `refcounter.New`
return value is no longer assignable to the dedicated type.

Verified with `cd client && CGO_ENABLED=1 go build .` (the failing CI
step) and the `TestReconcilePeerAllowedIPs` / refcounter / routemanager
tests.

## Issue ticket number and link

No public issue — fixes a `main` build break from a semantic merge
conflict between #6799 and the `ReconcilePeerAllowedIPs` change. Failing
run:
https://github.com/netbirdio/netbird/actions/runs/30330882389/job/90185591366

## Stack

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### Checklist
- [x] Is it a bug fix
- [ ] Is a typo/documentation fix
- [ ] Is a feature enhancement
- [ ] It is a refactor
- [ ] Created tests that fail without the change (if possible)

> By submitting this pull request, you confirm that you have read and
agree to the terms of the [Contributor License
Agreement](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT.md).

## Documentation
Select exactly one:

- [ ] I added/updated documentation for this change
- [x] Documentation is **not needed** for this change (explain why)

Internal build fix restoring a method on the AllowedIPs refcounter. No
public API, CLI, config, or behavior change.

### Docs PR URL (required if "docs added" is checked)
Paste the PR link from https://github.com/netbirdio/docs here:

N/A

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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Improved route reconciliation so all applicable allowed IP prefixes
are reliably re-applied for the correct peer.
* Prevented reconciliation from affecting routes assigned to other
peers.
* Improved handling of errors encountered while restoring multiple
routes, providing more consistent results.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

client/internal/routemanager/reconcile_test.go

@@ -54,7 +54,7 @@ func (m *reconcileWGMock) GetNet() *netstack.Net                      { return n
 func TestReconcilePeerAllowedIPs(t *testing.T) {
 	wg := &reconcileWGMock{}
 	m := &DefaultManager{wgInterface: wg}
-	m.allowedIPsRefCounter = refcounter.New[netip.Prefix, string, string](
+	m.allowedIPsRefCounter = refcounter.NewAllowedIPs(
 		func(_ netip.Prefix, peerKey string) (string, error) { return peerKey, nil },
 		func(netip.Prefix, string) error { return nil },
 	)

client/internal/routemanager/refcounter/allowedips.go

@@ -169,6 +169,27 @@ func (rm *AllowedIPsRefCounter) Flush() error {
 	return nberrors.FormatErrorOrNil(merr)
 }
 
+// ReapplyMatching calls apply for every prefix whose currently installed (active) peer satisfies
+// pred, holding the lock for the whole pass. It is used to re-push allowed IPs onto a peer whose
+// WireGuard entry was rebuilt (e.g. a lazy connection cycling idle->wake) without a matching
+// refcounter change, which would otherwise leave the prefix installed in the counter but missing
+// on the device. Only the active peer is considered — a prefix that lost its installed peer to a
+// failed swap is skipped here and reconciled by the next Increment/Decrement.
+func (rm *AllowedIPsRefCounter) ReapplyMatching(pred func(out string) bool, apply func(key netip.Prefix) error) error {
+	rm.mu.Lock()
+	defer rm.mu.Unlock()
+
+	var merr *multierror.Error
+	for prefix, e := range rm.entries {
+		if e.active != "" && pred(e.active) {
+			if err := apply(prefix); err != nil {
+				merr = multierror.Append(merr, err)
+			}
+		}
+	}
+	return nberrors.FormatErrorOrNil(merr)
+}
+
 // pickSurvivor deterministically selects a peer still referencing the prefix. WireGuard cannot do
 // multipath for a single prefix, so any surviving peer is a valid winner; the choice is made stable
 // (lowest peerKey) for predictable behavior and testability.